The Effects of a Brief Mindfulness Intervention on Emotional Responses and the Moderating Role of Interoception

Participants are asked to rate adjectives regarding their current mood (positive and negative) at two time points (baseline and after body scan or active control intervention) on a questionnaire. Change scores are calculated (post- minus pre-scores).

Instrument: Positive and Negative Affect Scale (PANAS) by Watson, Clark, and Tellegen (1988) is a self-report questionnaire that consists of two 10-item scales to measure both positive and negative affect. Each item is rated on a 5-point scale of 1 (not at all) to 5 (very much). Range for sum score of positive/negative affect: 10-50. For positive affect higher scores are better; for negative affect lower scores are better.

Participants are asked to rate how stressed they feel at the moment at two time points (baseline and after body scan or active control intervention) on a questionnaire (VAS: item ranges from 0 (not stressed at all) - 100 (very stressed). Change scores are calculated (post- minus pre-scores). More negative change scores are better since it indicates a stronger stress reduction (maximum reduction: -100). Higher positive change scores are worse since this indicates an increase in perceived stress (maximum increase: +100). Range of change scores: -100 - +100).

Heart rate variability (HRV) describes the variations between two successive heart beats and is considered a measure for cardiac adaptation to internal and external stimuli. HRV is considered an important transdiagnostic biomarker of health. HRV is frequently quantified using time- domain measures such as the standard deviation of NN intervals (SDNN) and the root mean square of successive differences between normal heartbeats (RMSSD). For HRV levels higher scores are better

The heartbeat perception task (Schandry, 1981) encompasses several trials in which participants are instructed to silently count their heartbeats and report the number they counted after each trial. Reported and actual number of heart beats (as assessed by ECG) will be used to calculate a heartbeat detection index (error score).

The State-Trait-Anxiety-Depression-Inventory (STADI) (Laux, L. Hock, M., Bergner-Köther, R., Hodapp, V. & Renner, K., 2013) measures participants' state anxiety (10 items) and state depression (10 items) severity. Each item can be answered on a 4-point-scale from 1 (not at all) - 4 (very much). Sum scores are calculated and range from 10-40 for each scale (depression and anxiety). Lower scores indicate lower severity (i.e., less negative mood).